Energy relaxation dynamics of photofragments measured by probe beam deflection technique: Photodissociation of CF3I at 266 nm

Energy relaxation dynamics of photofragments produced from photodissociatio n of trifluoromethyl iodide (CF3I) in argon at 266 nm was studied by means of a time-resolved probe beam deflection (PBD) technique. It was found that the PBD transients observed in Ar environment consist of two heat-releasin g (via collisional relaxation) processes that can be assigned to translatio nal-to-translational (T-T) and vibrational-to-translational (V-T) energy tr ansfers of photofragments. From the relaxation times and the fractions of t he two processes, 15% of the excess energy from photodissociation was found to be partitioned into vibrational modes of CS radicals while the remainin g 85% goes to translation. In addition, the intermolecular V-T energy-trans fer rate constant between CF3 and Ar was determined to be similar to 8.0 x 10(2) s(-1) Torr(-1). Electronic to translational (E-T) energy transfer fro m the spin-orbit excited iodine fragment, I*(P-2(1/2)), to the medium was n ot observed in the time domain employed in this study, unless oxygen, a wel l-known I* quencher, was added to facilitate the transfer process. An excel lent agreement between the obtained results and previously reported photofr agment translational spectroscopy results indicates that the energy relaxat ion processes of photofragments as well as energy partitioning of excess en ergy can be studied by the PBD method presented in this study.